Engine cooling system

Abstract

A flow control valve is located in a coolant circuit that extends through an engine. The flow control valve is operated in accordance with a control mode selected from a full closing control mode, a full opening control mode, and a feedback control mode. When switching from one control mode to another, the flow control valve is controlled in accordance with a transitional control procedure selected from different types of transitional control procedures. The transitional control procedure to be performed is selected depending on which control modes are performed before and after the control mode switching and/or the current condition of the engine. Transitional controlling of the flow control valve is thus appropriately conducted.

What is claimed is:  
     
       1. An engine cooling system, comprising: 
       a coolant circuit, which extends through an engine, wherein coolant flows in the coolant circuit;  
       a radiator, which is located in the coolant circuit, wherein the radiator cools the coolant that flows in the coolant circuit;  
       a flow control valve, wherein the flow control valve regulates the amount of the coolant that passes through the radiator; and  
       a controller, which controls the flow control valve for adjusting the temperature of the coolant that flows in the engine, wherein the controller controls the flow control valve in accordance with a control mode selected from different types of control modes, and wherein the controller performs a transitional control procedure selected from different types of transitional control procedures when switching from one control mode to another.  
     
     
       2. The system according to  claim 1 , wherein the controller selects the transitional control procedure to be performed depending on which control modes are performed before and after the control mode switching. 
     
     
       3. The system according to  claim 2 , wherein the control modes include a full opening control mode in which the flow control valve is maintained in a fully open state, a full closing control mode in which the flow control valve is maintained in a fully closed state, and a feedback control mode in which the opening size of the flow control valve is controlled in a feedback manner such that the temperature of the coolant that flows in the engine seeks a predetermined target value. 
     
     
       4. The system according to  claim 3 , wherein the feedback control mode is one of different types of control modes that set different target temperatures for the coolant. 
     
     
       5. The system according to  claim 1 , wherein the controller selects the transitional control procedure to be performed depending on the current condition of the engine, when switching from one control mode to another. 
     
     
       6. The system according to  claim 1 , wherein the different types of transitional control procedures include a control procedure in which the opening size of the flow control valve is gradually changed to a size suitable for the control mode to be performed after the control mode switching, and a control procedure in which the opening size of the flow control valve is rapidly changed to a size suitable for the control mode to be performed after the control mode switching. 
     
     
       7. The system according to  claim 1 , wherein the different types of control modes include a full opening control mode in which the flow control valve is maintained in a fully open state, and the controller selects the transitional control procedure to be performed depending on the current condition of the engine, when switching to the full opening control mode. 
     
     
       8. The system according to  claim 7 , wherein the different types of transitional control procedures include a transitional control procedure in which the opening size of the flow control valve is gradually changed to a size corresponding to the fully open state, and a transitional control procedure in which the opening size of the flow control valve is rapidly changed to the size corresponding to the fully open state. 
     
     
       9. The system according to  claim 7 , wherein the controller selects and executes a transitional control procedure in which the opening size of the flow control valve is gradually changed to a size corresponding to the fully open state if the engine is being warmed up, when switching to the full opening control mode. 
     
     
       10. The system according to  claim 7 , wherein the controller selects and executes a transitional control procedure in which the opening size of the flow control valve is rapidly changed to a size corresponding to the fully open state if the cooling system has a problem, when switching to the full opening control mode. 
     
     
       11. The system according to  claim 1 , wherein: 
       the different types of control modes include a feedback control mode in which the opening size of the flow control valve is controlled in a feedback manner such that the temperature of the coolant that flows in the engine seeks a predetermined target value;  
       the controller in the feedback control mode computes a target opening size of the flow control valve by correcting a basic opening size in accordance with a correction value, the basic opening size being determined depending on the operational state of the engine, the correction value being determined depending on the temperature of the coolant; and  
       the controller selects and executes a transitional control procedure in which the opening size of the flow control valve is gradually changed to the basic opening size, when switching to the feedback control mode.  
     
     
       12. The system according to  claim 1 , wherein the different types of control modes include a full closing control mode in which the flow control valve is maintained in a fully closed state, and the controller selects the transitional control procedure to be performed depending on the current condition of the engine, when switching from the full closing control mode to a different control mode. 
     
     
       13. The system according to  claim 12 , wherein the different types of transitional control procedures include a transitional control procedure in which the opening size of the flow control valve is gradually changed from a size corresponding to the fully closed state to a size suitable for the control mode to be performed after the control mode switching, and a transitional control procedure in which the opening size of the flow control valve is rapidly changed from the size corresponding to the fully closed state to the size suitable for the control mode to be performed after the control mode switching. 
     
     
       14. The system according to  claim 12 , wherein the controller selects and executes a transitional control procedure in which the opening size of the flow control valve is gradually changed from a size corresponding to the fully closed state to a size suitable for the control mode to be performed after the control mode switching if the engine is being warmed up, when switching from the full closing control mode to the different control mode. 
     
     
       15. The system according to  claim 12 , wherein the controller selects and executes a transitional control procedure in which the opening size of the flow control valve is rapidly changed from a size corresponding to the fully closed state to a size suitable for the control mode to be performed after the control mode switching if the cooling system has a problem, when switching from the full closing control mode to the different control mode. 
     
     
       16. The system according to  claim 1 , wherein: 
       the different types of control modes include a feedback control mode in which the opening size of the flow control valve is controlled in a feedback manner such that the temperature of the coolant that flows in the engine seeks a predetermined target value, and a large opening size control mode in which the opening size of the flow control valve is maintained at a size larger than a size suitable for the feedback control mode; and  
       the controller selects and executes a transitional control procedure in which the opening size of the flow control valve is rapidly changed to the size suitable for the large opening size control mode, when switching from the feedback control mode to the large opening size control mode.  
     
     
       17. The system according to  claim 16 , wherein the controller switches from the feedback control mode to the large opening size control mode when the cooling system has a problem. 
     
     
       18. The system according to  claim 1 , wherein: 
       the control modes include different types of feedback control modes;  
       in each of the feedback control modes, the controller controls the opening size of the flow control valve in a feedback manner such that the temperature of the coolant flowing in the engine seeks a predetermined target value that is different from the target values of the other feedback control modes; and  
       the controller selects the transitional control procedure to be performed depending on which feedback control modes are performed before and after the control mode switching.  
     
     
       19. The system according to  claim 18 , wherein the different types of feedback control modes include at least a first feedback control mode and a second feedback control mode, and the target temperature of the coolant in the first feedback control mode is higher than the target temperature of the coolant in the second feedback control mode. 
     
     
       20. The system according to  claim 19 , wherein the controller selects and executes a transitional control procedure in which the opening size of the flow control valve is changed first to a size corresponding to a fully open state and then to a size suitable for the second feedback control mode, when switching from the first feedback control mode to the second feedback control mode. 
     
     
       21. The system according to  claim 20 , wherein, in the selected transitional control procedure, the controller maintains the flow control valve in the fully open state until the temperature of the coolant drops to a value larger than the target temperature of the second feedback control mode by a predetermined margin. 
     
     
       22. The system according to  claim 19 , wherein the controller switches from the first feedback control mode to the second feedback control mode after a prescribed condition based on the operational state of the engine has been met consecutively for multiple times. 
     
     
       23. The system according to  claim 19 , wherein the controller selects and executes a transitional control procedure in which the opening size of the flow control valve is changed first to a size corresponding to a fully closed state and then to a size suitable for the first feedback control mode, when switching from the second feedback control mode to the first feedback control mode. 
     
     
       24. The system according to  claim 23 , wherein, in the selected transitional control procedure, the controller maintains the flow control valve in the fully closed state until the temperature of the coolant rises to a value smaller than the target temperature of the first feedback control mode by a predetermined margin. 
     
     
       25. An engine cooling system, comprising: 
       a coolant circuit, which extends through an engine, wherein coolant flows in the coolant circuit;  
       a radiator, which is located in the coolant circuit, wherein the radiator cools the coolant that flows in the coolant circuit;  
       a flow control valve, wherein the flow control valve regulates the amount of the coolant that passes through the radiator; and  
       a controller, which controls the flow control valve for adjusting the temperature of the coolant that flows in the engine, wherein the controller controls the flow control valve in accordance with a control mode selected from different types of control modes, the control modes include a first control mode in which the opening size of the flow control valve is maintained at a predetermined size, a second control mode in which the opening size of the flow control valve is maintained at a size smaller than the size of the first control mode, and a feedback control mode in which the opening size of the flow control valve is controlled in a feedback manner such that the temperature of the coolant that flows in the engine seeks a predetermined target value;  
       the controller controls the flow control valve in accordance with a transitional control procedure selected from different types of transitional control procedures when switching from one control mode to another; and  
       the controller selects the transitional control procedure to be performed depending on which control modes are performed before and after the control mode switching and/or the current condition of the engine.  
     
     
       26. A method for controlling an engine cooling system, wherein the system includes a coolant circuit that extends through an engine, the method comprising: 
       cooling coolant that flows in the coolant circuit with a radiator located in the coolant circuit;  
       regulating the amount of the coolant that passes through the radiator with a flow control valve;  
       controlling the flow control valve in accordance with a control mode selected from different types of control modes; and  
       controlling the flow control valve in accordance with a transitional control procedure selected from different types of transitional control procedures, when switching from one control mode to another.